1. Field of the Invention
The present invention relates to sustained release tablets including any of a wide array of pharmaceutical products and an excipient.
2. Description of the Related Art
Many attempts have been made in the pharmaceutical art to provide a composition which would enable the production of sustained release tablets. These attempts have produced compositions which are able to release pharmaceutical agents over a long period of time. However, such release has not been constant. Rather, prior art sustained release compositions generally release a disproportionate amount of their pharmaceutical agent quickly after ingestion by a patient. This results in a quick spike in the level of medication in the patient's bloodstream. Such a delivery method may be desirable where the pharmaceutical is intended to alleviate particular symptoms of a patient. However, there are many instances where a spike in the medication level in a patient is undesirable, as where pharmaceuticals are used to treat a chronic condition. Further, extended release of biologically active drugs is highly desirable for drugs that have characteristically short half lives.
Monolithic systems, composed of hydrophobic polymers and other excipients, are commonly used for extended release dosage forms because they are not costly or difficult to produce. However, such systems often provide a square-root-of-time (sqrt) kinetics (i.e. the amount of pharmaceutical agent released is proportional to the square root of the time since the drug was ingested). There are several ways to improve the release kinetics of extended release dosage forms. Incorporation of hydrophilic polymers into monolithic matrices modifies square root kinetics due to the swelling of the polymer. In particular, monolithic matrix systems controlled by the swelling/erosion processes of hydrophilic polymers can improve the pharmaceutical agent kinetics. However, even in these systems, the release rate of the pharmaceutical agent generally varies significantly with time.
Hydrophilic polymers alone have also been investigated for controlled drug release. The hydrophilic polymers such as hydroxypropylmethyl cellulose (HPMC) and polyvinylalcohol (PVA), which form gels upon contact with water and erode slowly, have been utilized for oral drug delivery systems. Cross-linked poly(ethylene oxide) has also been investigated for controlled drug delivery. However, attempts to use these materials to produce a constant, controlled, sustained drug release have thus far proven ineffective.